The purpose of this proposal is to determine, in serum-free culture conditions, the extent to which cartilage matrix synthesis and assembly can be regulated by thyroxine, growth hormone, parathyroid hormone, somatomedin and insulin. The chondrocytes to be studied are adult mammalian cells shown to be synthesizing the marker molecules to be used in this study, keratan sulfate and type II collagen. The techniques to be applied in carrying out this study include proteoglycan extraction and fractionation, collagen peptide analysis, DNA determination, incorporation of radio-precursors to glycosaminoglycan and collagen, quantification of individual glycosaminoglycan species, and tissue culture of adult rabbit articular cartilage chondrocytes. The significance of this study is that the adult chondrocyte physiology will be examined with specific reference to the control of mature cartilage-like extracellular matrix synthesis. The delineation and subsequent manipulation of conditions for synthesis of a true cartilage matrix will contribute to understanding more fully the loss of chondrocyte homeostasis during arthritis. Defined conditions for cartilage synthesis will also contribute to understanding cartilage repair and increasing the potential for cartilage transplantation.